Cryogenic fluid, such as liquefied natural gas, can be heated in a submerged combustion vaporizer (SCV). The SCV includes heat exchanger tubing and a water tank in which the tubing is submerged. The cryogenic fluid flows through the tubing. The SCV further includes a burner that fires into a duct system. The duct system has perforated sections, known as sparger tubes, that direct the burner exhaust to bubble upward through the water in the tank. The exhaust then heats the water and the submerged tubing so that the cryogenic fluid flowing through the tubing also becomes heated. Nitrogen oxides (NOx) in the exhaust are carried upward from the tank through a flue and discharged into the atmosphere with the exhaust.